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        console.log(bodyElement);   //返回文档的body元素

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        console.log(htmlElement);   //返回文档的html元素

        var titleElement = document.title;
        console.log(titleElement);  //返回文档的title元素

        var fromElement = document.forms;
        console.log(fromElement);   //返回文档的form元素

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        console.log(imageElement);   //返回文档的image元素
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